DNA Molecular Typography (IMAGE) Boston University Caption The many topographical levels of a chromosome. Genomic DNA is shown streaming out from a chromosome (left), progressively unfolding as chromatin, the 30-nm filament, nucleosomes, the DNA double helix, and finally the letters representing the nucleotide sequence. Although it is the molecular topography of the DNA helix that is recognized by proteins, current methods of genome analysis mostly focus on the order of nucleotides. Credit NHGRI Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.